RU2127482C1 - Method and device for exciting oscillations in electric circuit - Google Patents

Abstract

FIELD: generation of high-frequency damped oscillations; welding engineering. SUBSTANCE: method involves generation of oscillations by varying signal controlling excitation of oscillations in which series of current and voltage resonance is formed by shock excitation of electric circuits and generation of harmonics of higher order than that of fundamental oscillation in them. Device implementing this method has high- frequency transformer, thyristor switch, power supply, pulse transformer, resistor, phase-shifting unit, two capacitors, and inductance coil. EFFECT: increased power of electric oscillations which can greatly increase power capacity of welding apparatus. 2 cl, 4 dwg

Description

 The invention relates to a method for generating damped high-frequency oscillations and can be applied, in particular, in welding equipment, as an oscillator for excitation and stabilization of the welding arc.

 The known method, selected as an analogue "Method of shock excitation of oscillations in the electrical circuit" described in AS N 292592 C. H 03 B 11/08, characterized in that for the shock excitation of vibrations in the electrical circuit, an explosion of a metal wire is used. Moreover, in order to accurately fix the moment of explosion of the electric circuit, the explosion of the wire is initiated by a laser light beam. Using this method will increase the power of the excited oscillations, because thicker wire can be used without impairing the time characteristics.

 A known device selected as an analogue "Device for exciting an oscillatory circuit" described in the application of Germany N 3733943, class. H 03 B 11/04, characterized in that the oscillating LC circuit is connected via a controlled key to a direct current source. The key controlled by the control circuit, depending on the signal processing of the oscillating circuit, oscillates in the circuit.

 The disadvantage of the presented analogue is that the connected oscillatory circuit when it is shock-excited, develops weak electrical vibrations in power, as well as the complexity of the industrial applicability of the method.

 The closest in technical essence and the achieved positive effect to the claimed method is selected as a prototype "Method for excitation of oscillatory circuits described in the application of Germany N 3733943, CL H 03 B 11/04. The method of excitation of oscillations in the electrical circuit, which consists in oscillation generation, by regulating the signal that controls the excitation of oscillations.

 Essential for the prototype is the connection of the oscillating LC circuit in series or parallel to the DC source through a controlled key. The controlled key, depending on the signal processing of the oscillatory circuit, disconnects and connects the oscillatory circuit to the power source, thereby exciting the oscillatory circuit, and the control circuit determines the degree of damping of the oscillatory circuit.

 The closest in technical essence and the achieved positive effect to the claimed device is selected as a prototype "Generator of excitation of oscillations" described in US patent N 4837525, class. NKI 331-165.

 An oscillation excitation device in an electrical circuit containing a high-frequency transformer, the end of the primary winding of which is connected to the first output of the thyristor switch, the second end of which is connected to the first output of the first capacitor, the first output of the power source and to the end of the secondary winding of the pulse transformer, the beginning of which is connected through a resistor to thyristor switch control electrode.

 The disadvantage of the prototype presented is that in the connected oscillatory circuit, when it is shock excitation, insufficient oscillation power occurs. For example, when using the circuit as an oscillator, the latter, upon impact excitation, develops insufficient power for excitation and stabilization of the welding arc.

 The technical result of the invented method is to obtain powerful electric oscillations in the circuits, the use of which in an oscillator made in the form of the invented device, the welding machine will increase its power by several times, respectively, the degree of ionization of the electric arc gap.

где U(ωt) - напряжение ударного возбуждения контуров;
A - амплитуда переменного напряжения;
ω - круговая частота основной гармоники;
α - амплитуда резонанса напряжений;
n - номер гармоники;
ψ - фаза основной гармоники.The technical result is achieved due to the fact that in the method of excitation of oscillations in the electric circuit, which consists in generating oscillations by regulating the signal that controls the excitation of oscillations, in contrast to the prototype, a sequence of current resonance and voltage resonance is formed in electric circuits by shock excitation and generation in them there are harmonics of a higher order than the main oscillations, the amplitude of which is determined in accordance with the dependence:

where U (ωt) is the shock excitation voltage of the circuits;
A is the amplitude of the alternating voltage;
ω is the circular frequency of the fundamental;
α is the amplitude of the voltage resonance;
n is the number of harmonics;
ψ is the phase of the fundamental harmonic.

 The technical result is achieved due to the fact that in the device for exciting oscillations in an electric circuit containing a high-frequency transformer, the end of the primary winding of which is connected to the first output of the thyristor switch, the second output of which is connected to the first output of the power source and to the end of the secondary winding of the pulse transformer, the beginning of which through a resistor is connected to the control electrode of the thyristor switch, unlike the prototype, a phase-shifting unit and thyristor switch are introduced into it p is symmetrical, and the second output of the first capacitor is connected to the beginning of the primary winding of the high-frequency transformer and through the second capacitor is connected to the first output of the inductance, the second output of which is connected to the second output of the power source and to the first output of the phase-shifting unit, the second output of which is connected to the first output of the source power supply and to the end of the primary winding of a pulse transformer, the beginning of which is connected to the third terminal of the phase-shifting unit.

The essence of the invention lies in the fact that in series-connected circuits connected to an AC voltage source, by generating a sequence of resonances by shock excitation of the circuits, a shock excitation voltage with a wide frequency spectrum is created. In this voltage, there are frequencies f ₁ and f ₂ close to the eigenfrequencies of both oscillatory circuits, on which a sequence of resonances is carried out, first the resonance of the currents, then the resonance of the voltages.

 The essence of the invention lies in the fact that the invented method and device for its implementation provides the formation on the primary winding of a high-frequency transformer voltage, the magnitude of which is K-times greater than the voltage of the alternating power source, K - is determined by the quality factor of the serial circuit. This will significantly increase the oscillation power in the high-frequency transformer. The use of the invented device as an oscillator of a welding machine significantly increases the ionization power of the arc gap. The control signal shifts the phase of the AC cosine wave, which controls the oscillation power in the high-frequency transformer, respectively, the ionization power of the arc gap.

 In FIG. 1 is a timing diagram of the operation of a method for exciting oscillations in an electrical circuit, where V (ωt) is an alternating voltage; U (ωt) is the voltage of shock excitation of oscillations of the circuit; α is the amplitude of the voltage resonance, ψ is the phase of the fundamental harmonic is zero.

 In FIG. 2 is a fragment of a shock excitation voltage diagram of the circuit of FIG. 1. Volumes A and B show a sequence of resonances.

 In FIG. 3 is a timing diagram of the operation of the method of FIG. 1 with phase control.

 In FIG. 4 shows an electrical circuit diagram of a device for shock excitation of vibrations in an electrical circuit. Moreover, the timing diagrams of the operation of the method correspond to the point Q of the device according to FIG. 4.

где фаза основной гармоники ψ = 0
Аналитически эту функцию можно представить, как сумму двух функций, т.е. первая - косинусоида
V(ωt) = Acosωt, (2)
где A - амплитуда переменного напряжения;
и вторая - биполярная последовательность прямоугольных импульсов с периодом, равным периоду косинусоиды, и аналитически представляема рядом Фурье, как

где α - амплитуда прямоугольных импульсов.The method is as follows. To implement a sequence of resonances, alternating voltage is applied to the series-connected parallel and series oscillatory circuits. Through a controlled key in a circuit of a parallel oscillatory circuit, shock excitation of the circuit is formed. As a result of this, a voltage U (ωt) according to FIG. 1 of complex shape and a wide spectral composition, the analytical expression of which corresponds to the dependence in the form of a Fourier series

where the phase of the fundamental harmonic ψ = 0
Analytically, this function can be represented as the sum of two functions, i.e. the first is a cosine
V (ωt) = Acosωt, (2)
where A is the amplitude of the alternating voltage;
and the second is a bipolar sequence of rectangular pulses with a period equal to the period of the cosine wave, and is analytically represented by the Fourier series, as

where α is the amplitude of the rectangular pulses.

 A series of resonances is formed on the harmonics newly formed as a result of shock excitation of vibrations, and the currents resonance first, since a controlled switch is installed in the parallel circuit, accordingly there is a path for direct current, then voltage resonance in the serial circuit is carried out.

According to FIG. 1 segment AB voltage U ω corresponds to the resonance of the currents, and the segment BC corresponds to the resonance of the voltage. Further, the curve CA ¹ (more precisely, the cosine wave) corresponds to the application of alternating voltage to series-connected circuits. And the segments A ¹ B ¹ and B ¹ C ¹ correspond to similar processes described above with a different polarity.

 In FIG. 2 shows a voltage fragment of shock excitation of vibrations in the circuits according to FIG. 1 in vols. A and B, showing the sequence of resonances.

From t. A to t. B, the damped cosine characterizes the resonance of the currents in a parallel circuit, carried out with a frequency f ₁ . Moreover, the resonance of the currents is carried out at the harmonic formed as a result of shock excitation of the circuits, the frequency of which is close to the natural frequency of the parallel circuit. The damping decrement is determined by the losses in the circuit and, mainly, by the closing time of the control key τ _s . After the end of the current resonance, the voltage resonance in the series oscillatory circuit begins. From t. B to t. C, a damped sine wave characterizes the resonance of stresses carried out with a frequency f ₂ . Moreover, the shift along the coordinate axis by the value of α characterizes the quality factor of the oscillatory process of a sequential circuit and is determined by the parameters of the circuit elements. The resonance of the voltages is carried out at the harmonic formed during shock excitation of the circuit, the frequency of which is close to the natural frequency of the sequential oscillatory circuit.

 The damping decrement is determined by losses in the series circuit.

 By changing the parameters of the oscillatory circuits, respectively, their natural frequencies, the frequencies at which the sequence of resonances is carried out change. In this case, the quality factor of the contours can be brought up to 100 units and higher.

 In FIG. 3 is a timing diagram of the operation of the method of FIG. 1 and 2 with a phase shift of the fundamental harmonic to the left, respectively, to the right.

 According to FIG. 3, the shape of the voltage of the shock excitation MNEO corresponds to the analytical dependence according to equation (1), for the case ψ = 0, and ensures the formation of the maximum voltage at resonance of the currents. When the fundamental harmonic is shifted to the left by ψ, the shape of the shock excitation voltage takes the form along the curve indicated by 1 MNKO, according to FIG. 3 and is analytically written according to equation (1). In this case, the voltage generated during current resonance decreases in proportion to the phase shift and, accordingly, is equal to OK, and the voltage generated during voltage resonance remains unchanged.

При этом напряжение, формируемое при резонансе токов, уменьшается до величины OL.When the fundamental harmonic is shifted by π / 2, the shape of the shock excitation voltage takes the form along the curve indicated by 2 MNLO, according to FIG. 3 and analytically recorded as

In this case, the voltage generated by the resonance of the currents decreases to the value of OL.

 When the fundamental harmonic is shifted by ψ to the right, the shape of the shock excitation voltage takes the form according to the curve indicated by 3 MNKO. In this case, the voltage value generated by resonance of the currents corresponds to the value of KO according to FIG. 3.

 An apparatus for implementing the method illustrated in FIG. 1 and 2 shown in FIG. 4 includes an AC voltage source 1, which is connected to a phase-shifting unit 2, with an inductor 3, a capacity of 4 and parallel connected by a capacity of 5 and a high-frequency 6 transformer, which is connected to an AC voltage source 1 through a symmetric 7 thyristor switch, and the output of the phase-shifting 2 blocks through a pulse 8 transformer and resistor 9 is connected to the control electrode of the symmetric 7 thyristor switch. Moreover, the secondary winding of the high-frequency transformer 6 has output terminals 10 to which the load is connected. The phase shifting unit 2 contains a series-connected resistor 11, a potentiometer 12 and a capacitor 13, to the midpoint of which a symmetrical 14 dynistor is connected.

 Capacitance 5 and high-frequency transformer 6 form a parallel oscillatory circuit in which current resonance is formed, and inductance 3, capacitance 4 and capacitance 5 form a series oscillatory circuit in which voltage resonance is formed.

где L₆ - индуктивность высокочастотного 6 трансформатора;
C₅ - емкость конденсатора 5 согласно фиг. 4.The device according to FIG. 4 works as follows. An alternating voltage source 1 generates a voltage that is divided by a capacitive divider in a series oscillatory circuit in proportion to capacitances 4 and 5, and at a point corresponds to equation (2). The phase-shifting 2 block through the dinistor 14 forms a short pulse, which, through the pulse transformer 8 and resistor 9, enters the control electrode of the symmetric 7 thyristor switch. The thyristor 7 switch, including, generates shock excitation of a parallel oscillatory circuit, providing a circuit for direct current through the primary winding of the high-frequency 6 transformer. In this case, there will be a resonance of the currents and the voltage from T. A will move to T. B according to the diagram of FIG. 2 for the time τ _s , which corresponds to the closing time of the thyristor 7 switch. The resonance of the currents will take place at a frequency

where L ₆ is the inductance of the high-frequency 6 transformer;
C ₅ is the capacitance of the capacitor 5 according to FIG. 4.

где L₃ - индуктивность элемента 3 схемы согласно фиг. 4;
C₄ и C₅ - емкости конденсаторов 4 и 5 схемы согласно фиг. 4,
Декремент затухания колебательного процесса в последовательном колебательном контуре определяется потерями в этом контуре. Величина напряжения BC диаграммы согласно фиг. 1 определяется добротностью контура и зависит от параметров индуктивности 3 и емкостей конденсаторов 4 и 5. Все диаграммы, представленные на фиг. 1 ... фиг. 3 соответствуют напряжению в т. Q устройства согласно фиг. 4. Далее, при смене полярности переменного напряжения в последовательно включенных колебательных контурах протекают процессы, аналогичные вышеописанным.After the thyristor switch closes, there will be a resonance of voltages in the series circuit. In this case, the voltage from T. B will move to T. C according to the diagram of FIG. 2. The frequency of the resonance voltage is defined as

where L ₃ is the inductance of the circuit element 3 according to FIG. 4;
C ₄ and C ₅ are capacitances of capacitors 4 and 5 of the circuit according to FIG. 4,
The attenuation decrement of the oscillatory process in a sequential oscillatory circuit is determined by the losses in this circuit. The voltage value BC of the diagram according to FIG. 1 is determined by the quality factor of the circuit and depends on the parameters of the inductance 3 and capacitances of the capacitors 4 and 5. All the diagrams shown in FIG. 1 ... fig. 3 correspond to the voltage in t. Q of the device according to FIG. 4. Further, when the polarity of the alternating voltage is changed, processes similar to those described above proceed in series-connected oscillatory circuits.

 By adjusting the variable 12 resistor in the phase-shifting 2 block, the phase shift of the damped pulses of the symmetric 7 thyristor switch relative to the fundamental harmonic of the oscillations according to FIG. 3, the voltage applied to the primary winding of the high-frequency transformer 6 can be adjusted; accordingly, the power of high-frequency oscillations can be controlled to some extent from the output terminals 10 of the device according to FIG. 4.

 The positive effect of the invention lies in the fact that the method and device for its implementation provide the formation on the primary winding of a high-frequency transformer voltage, the value of which is K times the magnitude of the voltage of the AC power source, K - is determined by the quality factor of the circuit. This will significantly increase the oscillation power in the high-frequency transformer. The use of the invented device as an oscillator of a welding machine significantly increases the ionization power of the arc gap. The control signal shifts the phase of the alternating voltage, which regulates the power on the high-frequency transformer, respectively, the degree of ionization of the arc gap.

Literature
1. USSR author's certificate N 292592, H 03 B 11/08, 1975.

 2. Application of Germany N 3733943, H 03 B 11/04, 1989.

 3. US patent N 4837525, 331 - 165, 1989.

 4. Bessonov L. A. Theoretical foundations of electrical engineering. - M.: Higher School, 1973, p. 135 - 142.

Claims (2)

 1. The method of excited oscillations in electrical circuits, which consists in generating oscillations by regulating the signal that controls the excitation of oscillations, characterized in that they act on the parallel and serial circuits to generate their shock excitation and create harmonics of a higher order than fundamental oscillations on which the sequence of current resonance and voltage resonance flows.  2. An oscillation excitation device in an electric circuit containing a high-frequency transformer, the end of the primary winding of which is connected to the first output of the thyristor switch, the second output of which is connected to the first output of the first capacitor, the first output of the power source and to the end of the secondary winding of the pulse transformer, the beginning of which is through a resistor connected to the control electrode of the thyristor switch, characterized in that a phase-shifting unit is inserted into it, the thyristor switch is made simme primary, and the second output of the first capacitor is connected to the beginning of the primary winding of the high-frequency transformer and through the second capacitor is connected to the first output of the inductor, the second output of which is connected to the second output of the power source, to the first output of the phase-shifting unit, the second output of which is connected to the first output of the power source and to the end of the primary winding of the pulse transformer, the beginning of which is connected to the third terminal of the phase-shifting unit.

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